Kyoko Kotani

Bidirectional optical subassembly with prealigned silicon microlens and laser diode

We have succeeded in developing a low-cost bidirectional optical subassembly chip using a silicon microlens for fiber-to-the-home application. The main optical elements of the bidirectional function were automatically aligned and integrated on a silicon optical bench. The cost of subassembly was markedly lowered both by reducing the part number and simplifying the assembly process. The prototype bidirectional optical component was successfully fabricated on the basis of the proposed chip. A receiver minimum sensitivity of -28.5 dBm was experimentally demonstrated even at 75 degC

Design of Polarization-Independent Si-Wire-Waveguide Wavelength Demultiplexer for Optical Network Unit

We report the design of a compact wavelength demultiplexer using a Si wire waveguide as an optical network unit. We use a Mach–Zehnder lattice interferometeric filter structure to attain a flat-top response. The large wavelength dispersion of the Si wire waveguide requires special design considerations for widely separated wavelength channels. Preliminary experimental results obtained by the device fabricated in a silicon-on-insulator wafer showed a flat-top filter response.

Scalability analysis of diffractive optical element-based free-space photonic circuits for interoptoelectronic chip interconnections

An interchip free-space optical interconnection module is investigated to solve the pin-input-output bottleneck at the interface of silicon integrated circuits. The scalability of the photonic circuit is theoretically analyzed by use of the minimum feature size requirement of each diffractive element used. The study showed that interconnection densities of 1000-2000 channels/cm is possible for a 40-mm interconnection length with a 3-mm-thick optical substrate. Diffraction-limited imaging capability has been demonstrated using a fabricated prototype, confirming its applicability for interchip free-space interconnections. Photonic circuit insertion losses of -23.4 dB for TE polarization and -25.9 dB for TM polarization as well as a polarization-dependent loss of 2.5 dB are found to be caused primarily by a pair of binary linear gratings used for beam deflections. Design modifications aiming at insertion loss reduction and further improvement of tolerance capabilities are also discussed.

Surface-mountable silicon microlens for low-cost laser modules

A surface-mountable silicon microlens that can be passively aligned in a silicon V-groove is proposed. The microlens has a diffractive optical element on the end facet of a semicylindrical structure whose diameter is identical to that of a single-mode fiber (SMF). The experimental result of coupling efficiency between a distributed feedback laser diode and SMF shows low loss (-3.0 dB) as determined using the microlens. Monte Carlo simulations indicate that the microlens is suitable for low-cost and high-performance optical modules for metro networks.

A low-cost micro-BOSA using Si microlens integrated on Si optical bench for PON application

We propose single TO-CAN type bi-directional optical subassembly in which. LD, PD chips, filter and Si microlenses are passively integrated on Si optical bench. High performance such as minimum sensitivity of -28 dBm was experimentally demonstrated.

A low cost PON transceiver using single TO-CAN type micro-BOSA

A novel low-cost small-form-factor (SFF) optical transceiver using a micro-compact bi-directional optical sub-assembly (micro-BOSA) for passive optical network (PON) application is proposed. In this micro-BOSA, optical transmitting and receiving functions are incorporated in a single TO-CAN package. The BOSA is compact and its pin assignment provides fine connection to printed circuit board and fit in transceiver housing. Bi-directional optical transmission at 1.25Gbit/s with the receiver minimum sensitivity of -28.2dBm is demonstrated for the fabricated transceiver with the proposed micro-BOSA

Ultra compact optical subassembly using integrated laser diode and silicon microlens for low-cost optical component

We have succeeded in developing an ultra compact optical subassembly (OSA) that consists of a pre-aligned Si microlens and a laser diode (LD) integrated on a Si V-groove substrate with a footprint less than 1 mm by 1 mm. This OSA is small enough to be mounted on a TO-CAN package such as TO38, making the resulting optical component ultra compact in size and reducing the packaging process cost. A coupling efficiency better than -2.6 dB between the OSA and a single-mode fiber (SMF) has been experimentally confirmed. The experimental results show the OSAs applicability to metro networks, making the OSA a promising candidate for low-cost and high-performance optical components.

Compact bidirectional photonic circuit employing stacked multilayers of diffractive optical elements for fiber-to-the-home applications

In order to introduce optical fibers in the last one mile to the home, the realization of low cost photonic circuit is crucial. We propose a new concept of photonic circuit consisting of stacked multi-layers of diffractive optical elements. Wafer-scale alignment is expected to reduce fabrication cost of each photonic circuit. The first prototype demonstration of the photonic circuit is reviewed. The experimental results required further insertion loss improvement. To fulfill this need, we developed an optical CAD environment specifically targeted on telecommunication applications. The detail of the CAD environment as well as the second prototype experimental results are discussed.

Expanded application of silicon V-groove platform with silicon microlens

We propose new silicon microlens for low-cost optical packaging, suitable for surface-mount technology with silicon V-groove platform. Efficient coupling of -3 dB between DFB-LD and single-mode fiber confirmed the feasibility of the concept to metro applications.

Integration of silicon microlenses to light sources for datacom and telecom applications

Passive alignment between the light source and coupling lenses may be one of the crucial and yet challenging technical fields to produce low-cost optical modules for telecom and datacom applications. In our presentation, we report the current status of our integration technologies of both surface and edge emitting type lasers with coupling lenses. We propose surfacemountable silicon microlens whose diameter is identical to a conventional optical fiber. The microlens can be passively aligned in the silicon v-groove to realize beam coupling between an edge emitting laser diode and an optical fiber. Coupling efficiency of -3.2dB between distributed feed-back laser diode and a single-mode fiber was experimentally confirmed. Precise rod shape is fabricated by D-RIE technology. We also report monolithic integration of the silicon substrate and a surface-emitting light source accomplished by direct bonding technology. The corresponding collimating lens is fabricated on the back-surface of the same silicon substrate. Passive alignment between the light source and the corresponding lenses are ensured by using a double-view mask aligner with sub-micron accuracy.